The present invention relates to testing or monitoring apparatus in general, and more particularly to improvements in apparatus for monitoring accumulations (particularly streams) of flowable comminuted solid material. For example, the apparatus of the present invention can be utilized with advantage for the monitoring of a stream of pulverulent coal or another mineral, of a stream of ground food products or the like.
Heretofore known apparatus for monitoring the flow of a comminuted solid material comprise a vessel, a device which admits the stream of comminuted material into the vessel, and a device which directs a beam of radiation (e.g., a beam of light or a laser beam) across the path of the stream in the vessel. An evaluation of the beam (called analyzing beam) which has traversed the stream of comminuted material in the vessel renders it possible to ascertain certain characteristics of the corresponding portion of the stream. The stream admitting device normally comprises a pipe which is coaxial with the vessel at the locus of entry and delivers comminuted solid material in a compressed gaseous carrier medium. The end portion of the pipe is bent at right angles close to the locus of entry into the vessel, and such conventional apparatus further comprise an injector which admits compressed air into the pipe at a location close to the bend in the pipe and is intended to impart to the solid material energy in order to cause such material to flow in the vessel in a manner which is suitable for analysis. As a rule, the injector is coaxial with the straight portion of the pipe which extends into the vessel.
The aforediscussed conventional monitoring apparatus exhibit the drawback that the comminuted material tends to adhere to the pipe as well as to the vessel. This exerts an adverse influence upon the homogeneousness of the material in the region where the material is traversed by the analyzing beam so that the analysis can furnish misleading results.